Cells, Atoms and Molecules
Name 3 types of chemical bonds
• Covalent – forms when 2 non-metals share a pair of electrons
• Ionic – electrostatic attraction between oppositely charged ions
• Hydrogen – bond formed with a slightly positive hydrogen atom of a polar covalent
bond forms an electrostatic link with the more electronegative atom of a polar covalent
bond in the same or another molecule
State the relative strength of these bonds
Strongest Weakest
Covalent > Ionic > Hydrogen > non-polar
Non-Covalent interactions are individually weak but collectively strong.
Ionic bonds and hydrogen bonds are polar or hydrophilic.
Non-polar interactions are hydrophobic.
Describe how does salt dissolve in water
Water – A polar molecule that forms hydrogen bonds.
Water is a versatile solvent due to its polarity. When an ionic compound is dissolved in water, each
ion is surrounded by a sphere of water molecules called a hydration shell. Water can also dissolve
compounds made of non-ionic polar molecules. Even large polar molecules such as proteins can
dissolve in water if they have ionic and polar region.
Water dissolves salt by dissociating the ions in salt from each other. Because water is a polar
molecule, each of its ends holds a slight positive or negative electrical charge. These ends attract the
positive and negative ions in salt and pull them apart from each other.
The polarity of water comes from the differences in electronegativity in the atoms involved in the
bonding process. When covalently bonded atoms have a difference in electronegativity, the
electrons are shared unevenly in the bond and result in opposing slightly negative and positive
charged ends. In water, the positive end is composed of the hydrogen atoms and the negative end is
the oxygen atom. When interacting with sodium chloride - common table salt - the positive sodium
ion is drawn to the oxygen end of water and the negative chloride ion to the hydrogen end.
Convert simple examples of H+ and OH- concentrations to pH and Vice Versa
pH = -log10 [H+]
In any aqueous solution at 25ºC, the product of H+ and OH– is constant and can be written as
[H+][OH–] = 10–14
Name 3 types of chemical bonds
• Covalent – forms when 2 non-metals share a pair of electrons
• Ionic – electrostatic attraction between oppositely charged ions
• Hydrogen – bond formed with a slightly positive hydrogen atom of a polar covalent
bond forms an electrostatic link with the more electronegative atom of a polar covalent
bond in the same or another molecule
State the relative strength of these bonds
Strongest Weakest
Covalent > Ionic > Hydrogen > non-polar
Non-Covalent interactions are individually weak but collectively strong.
Ionic bonds and hydrogen bonds are polar or hydrophilic.
Non-polar interactions are hydrophobic.
Describe how does salt dissolve in water
Water – A polar molecule that forms hydrogen bonds.
Water is a versatile solvent due to its polarity. When an ionic compound is dissolved in water, each
ion is surrounded by a sphere of water molecules called a hydration shell. Water can also dissolve
compounds made of non-ionic polar molecules. Even large polar molecules such as proteins can
dissolve in water if they have ionic and polar region.
Water dissolves salt by dissociating the ions in salt from each other. Because water is a polar
molecule, each of its ends holds a slight positive or negative electrical charge. These ends attract the
positive and negative ions in salt and pull them apart from each other.
The polarity of water comes from the differences in electronegativity in the atoms involved in the
bonding process. When covalently bonded atoms have a difference in electronegativity, the
electrons are shared unevenly in the bond and result in opposing slightly negative and positive
charged ends. In water, the positive end is composed of the hydrogen atoms and the negative end is
the oxygen atom. When interacting with sodium chloride - common table salt - the positive sodium
ion is drawn to the oxygen end of water and the negative chloride ion to the hydrogen end.
Convert simple examples of H+ and OH- concentrations to pH and Vice Versa
pH = -log10 [H+]
In any aqueous solution at 25ºC, the product of H+ and OH– is constant and can be written as
[H+][OH–] = 10–14
